Understanding 80 Percent Lowers: What They Are and How to Use Them
Firearm enthusiasts increasingly turn to 80 percent lowers for custom builds, but understanding what they are and how to use them can make a huge difference in the outcome of your build.
In this guide, we’ll dive into what an 80 percent lower is, the benefits of using them, legal considerations, and a step-by-step look at how to complete an 80 percent lower for your own firearm build. While 80% lowers are no longer legal in California, we wanted to write this article to help anyone not in California that may be looking to upgrade or build their firearm.
What Is an 80 Percent Lower?
An 80 percent lower is a partially completed firearm receiver that requires additional machining before it can be used to build a functional firearm. These lowers are commonly used with AR-15s, Glocks, and other popular firearm models. The term “80 percent” refers to the fact that the lower receiver is about 80 percent complete, and the builder is responsible for finishing the remaining 20 percent.
Since it isn’t technically a firearm when purchased, an 80 percent lower doesn’t require a federal background check, though completing one at home may have legal implications (more on that later). The receiver is often made from polymer or aluminum, and once completed, it forms the basis for the remaining components in your firearm build.
Why Choose an 80 Percent Lower?
There are several reasons firearm builders choose 80 percent lowers for their projects:
Customization and Personalization
An 80 percent lower allows builders to create a firearm that’s uniquely their own. You have complete control over each part and accessory, from the jig you use for milling to the final finishes and optics.
Cost Savings
Completing an 80 percent lower at home can be more cost-effective than buying a fully assembled firearm, especially when sourcing parts and materials through a trusted retailer.
Privacy and Ownership Control
Since an 80 percent lower isn’t a complete firearm, you aren’t required to go through the same background checks and paperwork as you would with a complete firearm. This allows for a level of ownership privacy that many enthusiasts find appealing.
Learning Experience
Building a firearm from an 80 percent lower is an educational experience, allowing you to understand the inner workings of the firearm while gaining valuable gunsmithing skills.
Legal Considerations for 80 Percent Lowers
The legality of 80 percent lowers varies by state, so it’s essential to understand the laws in your area. While it’s generally legal to purchase an 80 percent lower in most parts of the U.S., some states have restrictions or requirements regarding the completion of the lower.
In California, for example, as of July 1, 2022, California law prohibits the sale, purchase, possession, transfer, or completion of 80% lower receivers.
How to Complete an 80 Percent Lower
Completing an 80 percent lower requires careful planning, the right tools, and a step-by-step approach to ensure accuracy and safety. Here’s an overview of the process:
Choose Your Material: Polymer or Aluminum
• Polymer Lowers: Easier to mill and more lightweight, ideal for those who want a quick and affordable build.
• Aluminum Lowers: Durable and long-lasting, suitable for those who want a professional-grade build with added stability.
Select Your Jig Kit
A jig is essential for completing an 80 percent lower accurately. It provides the guide you’ll follow to mill the receiver correctly.
Gather Your Tools
You’ll need some essential tools to complete your lower, including:
• A milling machine or drill press
• End mills and drill bits designed for firearms
• Clamps to secure the jig and lower during milling
• A vise to stabilize your work area
Our staff can advise you on the best tools for the job, especially if this is your first time working with an 80 percent lower.
Follow Step-by-Step Milling Instructions
• Secure the Lower in the Jig: Place the lower receiver in the jig and secure it with clamps.
• Drill Pilot Holes: Using the jig as a guide, drill pilot holes where necessary, following the jig’s instructions closely.
• Mill Out the Trigger Pocket: Use an end mill bit to remove material within the trigger pocket. Take your time and make shallow passes to avoid mistakes.
• Drill Safety Selector and Pin Holes: Complete the necessary holes for the safety selector and pins, ensuring alignment with your jig guide.
Tip: Milling an 80 percent lower can be a meticulous process, so it’s essential to go slow and check your work frequently.
Finish and Assemble Your Firearm
Once the milling is complete, you’re ready to finish and assemble your firearm. Choose quality parts and accessories to complete your build, such as a trigger assembly, grip, upper receiver, and magazine. We carry a variety of high-quality components and can help you select parts that fit your preferences.
Additional Tips for Working with 80 Percent Lowers
• Practice First: If it’s your first time, practice milling on scrap metal or polymer to get a feel for the process.
• Invest in Quality Tools: A quality jig and tools make a noticeable difference in the outcome, reducing the chance of errors.
• Inspect Your Work: After each stage, inspect your milling to ensure accuracy. Small mistakes can often be corrected early on with careful attention.
Route 66 Guns & Ammo: Your Partner in Custom Firearm Builds
At Route 66 Guns & Ammo, we’re committed to providing firearm enthusiasts across Barstow, Hesperia, Apple Valley, Phelan, and Victorville with everything needed for successful custom builds. Located conveniently between Las Vegas and Los Angeles, our shop carries a wide selection of lowers, tools, and expert advice.
Whether you’re interested in an AR-15 build, a Glock frame, or anything else our knowledgeable team is here to help you every step of the way. Visit Route 66 Guns & Ammo for everything you need to start building your custom firearm today.